As for a front-loading washing machine, when a drum driven by a variable frequency motor is unbalanced, the higher a rotation speed of the variable frequency motor is, the larger vibration and noise of the system are, thereby reducing service life of the front-loading washing machine. The variable frequency motor has load unbalance detection function, when a load such as the drum is found to be unbalanced, the vibration and noise of the system can be reduced by adjusting the rotation speed or changing the unbalanced state of the load.
The two conventional unbalance detection methods are as follows:
(1) A sensor can be adopted to detect whether the drum is balanced or not, however the sensor has high cost and is not easy to mount, thereby resulting in a high detection difficulty.
(2) Whether the drum is balanced or not can be judged according to the rotation speed or torque of the variable frequency motor during a low-speed operation phase and a high-speed operation phase. However, this method cannot achieve a dynamic unbalance detection while performing a static unbalance detection of the drum during the low-speed operation phase (the motor operates at a constant rotation speed). Since the drum operates at a high speed during the high-speed operation phase, performing the dynamic unbalance detection during the high-speed operation can make mechanical components inside the washing machine collide, resulting in damage to the washing machine.
From the above, there are problems in the prior art that cost is high, detection difficulty is high, the dynamic unbalance detection of the drum cannot be performed during the low-speed operation phase, and performing the dynamic unbalance detection during the high-speed operation will make the mechanical components inside the washing machine collide, resulting in damage to the washing machine.